Eight armed men held a bank manager at gunpoint and requested customers to "cooperate" with them before fleeing with Rs 13 lakh in Hooghly's Bandel on Tuesday morning.

The entire operation was over in 10 minutes. But not a single image of the robbers could be captured because the bank did not have any CCTV camera.

The eight-member gang entered the branch of Punjab and Sind Bank, about 60km from Calcutta, around 10.45am and spread out across the premises, police said.

The bank is on the ground floor of a three-storeyed building.

The police said there were 35 customers and eight employees, including the manager, when the gang entered the bank. "All of them whipped out guns, triggering panic among the customers," said Gopal Chaki, who was in the bank then to deposit money.

One of the robbers blocked the bank's main entrance while another overpowered the guard. Two of them "politely" requested the customers to cooperate with them by not raising an alarm.

While one of them held a gun to the manager's forehead, the others asked for the keys to the vault. "One of them stayed in my room holding a gun at me, while the rest proceeded to the vault along with the guard," said manager Anuj Kumar.

There was around Rs 7 lakh in the vault, which the robbers put in their bag. They picked up another Rs 6 lakh from teller counters.

"After they picked up all the money, the robbers locked all of us in the vault and fled," said Dhananjay Dey, the guard.

Before locking up the customers and bank officials inside the vault, the robbers took away their mobile phones so they could not alert the police.

"The robbers spoke very politely in Hindi. One of them urged us to cooperate with them. Another asked us to switch off our mobile phones and hand them over. They said they would not harm us if we kept quiet," Chaki recounted.

The robbers, however, did not take the second mobile phone that the manager had in his pocket.

The customers and bank employees were rescued after the manager alerted the cops with the second phone.

"The bank does not have a CCTV camera so we do not have the pictures of the robbers. However, we have collected finger prints. A CID team visited the bank. We will trace the robbers soon," said Koteswara Rao, deputy superintendent of police, Hooghly.

No one was arrested till Tuesday evening.